#include <bits/stdc++.h>
using namespace std;
string add(string str1, string str2)
{
    string str;
    int len1 = str1.length();
    int len2 = str2.length();
    if(len1 < len2)
    {
        for(int i = 1; i <= len2 - len1; i++)
           str1 = "0" + str1;
    }
    else
    {
        for(int i = 1; i <= len1 - len2; i++)
           str2 = "0" + str2;
    }
    len1 = str1.length();
    int cf = 0;
    int temp;
    for(int i = len1 - 1; i >= 0; i--)
    {
        temp = str1[i] - '0' + str2[i] - '0' + cf;
        cf = temp / 10;
        temp %= 10;
        str = char(temp + '0') + str;
    }
    if(cf != 0)  str = char(cf + '0') + str;
    return str;
}
int main() {
	string a[5005];
	a[0] = '1';
	a[1] = '1';
	int n;
	cin >> n;
	for(int i = 2; i <= n; i++) {
		a[i] = add(a[i - 1], a[i - 2]);
	}
	cout << a[n];
}
